The Japanese had developed a long-range flying boat, the Kawanishi H8K ('Emily') which entered production in 1941 and first saw operational use on the night of 4 March 1942 in a second raid on Pearl Harbor, known as 'operation K'. Since the target lay out of range for the flying boats, this audacious plan involved a refuelling by submarine at French Frigate Shoals, some 900 km north-west of Hawaii, en route. The raid was originally planned with five H8K planes. In the end just two planes from the Yokohama Kōkūtai (Naval Air Corps) attempted to bomb Pearl Harbor, but, due to poor visibility, did not accomplish any significant damage.

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